1. Field of the Invention
The present invention relates to a plasma display panel used as a flat display for a television receiver, a computer, and a like, and a method of manufacturing the plasma display panel (PDP), and more particularly, relates to an AC (Alternating Current) driving surface discharge type of plasma display panel and a method of manufacturing the AC driving surface discharge type of plasma display panel.
The present application claims priority of Japanese Patent Application No. 2001-191765 filed on Jun. 25, 2001, which is hereby incorporated by reference.
2. Description of Related Art
FIG. 7 is a perspective exploded view showing a schematic structure of a conventional AC driving surface discharge type of Plasma Display Panel (hereinafter referred to as PDP) 1 in that a part of the front insulation substrate 2 is cut out. FIG. 8 is a top view showing a state in that a front insulation substrate 2 of the PDP 1 is removed. FIG. 9 is an enlarged sectional view showing a section along a line A-Axe2x80x2 in FIG. 8. The PDP 1 is disclosed in Japanese Patent No. 3036496, Japanese Patent Application Laid-open No. Hei 11-202831, and a like.
In the PDP 1, as shown in FIG. 7 to FIG. 9, under the front insulation substrate 2, a plurality of pairs of sustaining electrodes 3a and sustaining electrodes 3b of each extending in a row direction (in a horizontal direction in FIG. 8) are arranged in a column direction (in a vertical direction in FIG. 8) at predetermined intervals so that a discharge gap 4 is put between each pair. The front insulation substrate 2 is made of soda lime glass or a like so as to have a thickness of 2 mm to 5 mm similarly to a back insulation substrate 8 which will be described later. Both of the sustaining electrode 3a and the sustaining electrode 3b are made up of transparent conductive thin films such as tin oxide, indium oxide, and ITO (Indium Tin Oxide) and form a surface discharge electrode pair 3.
A plurality of pairs of bus electrodes 5a and bus electrodes 5b are respectively formed on low surfaces of the plurality of pairs of sustaining electrodes 3a and sustaining electrodes 3b at one side of each end. The bus electrodes 5a and the bus electrodes 5b are made up of metal films such as thick films of silver, or thin films of aluminum or copper and are formed in order to make resistance values of the sustaining electrode 3a and the sustaining electrode 3b of which each electrical conductivity is low. Respective lower faces on which no sustaining electrode 3a and no sustaining electrode 3b and no bus electrode 5a and no bus electrode 5b are formed in the front insulation substrate 2 are covered by a dielectric layer 6 which is transparent. The dielectric layer 6 is made of low melting point glass of which a thickness is 10 xcexcm to 40 xcexcm. A protection layer 7 is formed on the lower face of the dielectric layer 6 in order to protect the dielectric layer 6 from ion impacts during discharge. The protection layer 7 is made of magnesium oxide or a like of which a secondary emission coefficient is large and of which a sputtering-resistance is good, and formed by vacuum deposition or a like so as to have a thickness of 0.5 xcexcm to 2.0 xcexcm.
On the other hand, a plurality of data electrodes 9 in stripe shapes extending in a column direction, namely, in a direction perpendicular to formation direction of the sustaining electrodes 3a and the sustaining electrodes 3b are formed at predetermined intervals. The data electrode 9 is made up of a silver film or a like. Respective upper faces of the data electrodes 9 and the back insulation substrate 8 on which no data electrodes 9 are formed are covered by a white dielectric layer 10. On the dielectric layer 9 except the data electrode 9, a plurality of division walls 13 for separating display cells 12 are formed in the column direction. The display cell 12 is a minimum unit for forming a display screen. In FIG. 8, an area surrounded by a dashed line indicates one of the display cells 12.
Three fluorescent layers 14R, 14G, and 14B for converting an ultraviolet ray which is generated by discharge of a discharge gas into three primary colors of red (R), green (G), and blue (B) of a visible light are formed on the upper face of the dielectric layer 8 on the data electrode 9 and on the side face of the division wall 13. The fluorescent layers 14R, 14G, and 14B are formed in order of the fluorescent layer 14R, the fluorescent layer 14G, and the fluorescent layer 14B sequentially repeatedly in the row direction. The fluorescent layers (not shown) for each converting the ultraviolet ray into a visible light of a same color are formed continuously in the column direction.
Each discharge gas space 15 is kept in each space formed by the lower face of the protection layer 7, each upper face of the fluorescent layers 14R, 14G, and 14B, and two division walls 13 adjacent to each other. The discharge gas space 15 is filled with a discharge gas such as xenon, helium, or neon, or mixed gas thereof under pressure of 20 kPa to 80 kPa. An area including the sustaining electrode 3a and the sustaining electrode 3b, the bus electrode 5a and the bus electrode 5b, the data electrode 9, the fluorescent layers 14R, 14G, and 14B and the discharge gas space 15 makes the display cell 12. When the size of the display cell 12 is 1.05 mm in the vertical direction (column direction) and 0.355 mm in the horizontal direction (row direction), the sustaining electrode 3a and the sustaining electrode 3b of which widths are 300 xcexcm to 500 xcexcm and of which thicknesses are 0.1 xcexcm to 2.0 xcexcm are made so as to have the discharge gap 4 of 50 xcexcm to 300 xcexcm therebetween.
Next, a method of forming the sustaining electrode 3a and the sustaining electrode 3b, and the bus electrode 5a and the bus electrode 5b included in the PDP 1 will be explained with reference to FIG. 10A to FIG. 10E. The sustaining electrode 3a and the sustaining electrode 3b are formed by a lift-off method shown in FIG. 10A to FIG. 10E. FIG. 10A to FIG. 10E are enlarged sectional views showing a side of the front insulation substrate 2 which is enlarged and is turned over up and down in a section along a line A-Axe2x80x2 in FIG. 8. First, as shown in FIG. 10A, a photosensitive dry film 21 is laminated on the front insulation substrate 2. The photosensitive dry film 21 includes a support film (not shown) and photosensitive resin (not shown) formed on the support film. Then, as shown in FIG. 10B, the photosensitive dry film 21 is exposed and developed to pattern the dry film 21. Then, as shown in FIG. 10C, a transparent conductive thin film 22 is formed on the photosensitive dry film 21 which is patterned. Then, as shown in FIG. 10D, the sustaining electrode 3a and the sustaining electrode 3b of predetermined shapes are obtained by removing the photosensitive dry film 21. Then, as shown in FIG. 10E, after pattern printing of silver paste (not shown) is applied onto the sustaining electrode 3a and the sustaining electrode 3b, the bus electrode 5a and the bus electrode 5b of predetermined shapes are obtained by annealing (for example, keeping 560xc2x0 C. for thirty minutes).
Now, an outline principle in which one display cell 12 emits in the PDP 1 will be explained. First, when a voltage signal for keeping discharge is applied to the sustaining electrode 3a and the sustaining electrode 3b, a discharge generates in the discharge gas space 15. Electrons which generate by this discharge are in collision with xenon atoms, helium atoms, neon atoms, or a like (hereunder, called only xenon atoms or a like), the xenon atoms or a like are excited or ionized. For example, excited xenon atoms generate ultraviolet rays of a vacuum ultraviolet area of 147 nm to 190 nm. The generated ultraviolet rays are irradiated to the fluorescent layer 14R, the fluorescent layer 14G, and the fluorescent layer 14B. The fluorescent layer 14R, the fluorescent layer 14G, and the fluorescent layer 14B to which the ultraviolet rays are irradiated respectively, generate a visible red light, a visible green light, and a visible blue light. The visible red light, the visible green light, and the visible blue are respectively reflected by the white dielectric layer 10, and then go out after passing through the protection layer 7, the dielectric layer 6, the sustaining electrode 3a, the sustaining electrode 3b, and the front insulation substrate 2.
On the other hand, the discharge which generates in the discharge gas space is stopped automatically, after electric charges are accumulated on a lower face of the dielectric layer 6. For example, when a positive pulse voltage is applied to the sustaining electrode 3a and a negative pulse voltage is applied to the sustaining electrode 3b as voltage signal, electrons which generate by the discharge in the discharge gas space 15 move to the sustaining electrode 3a and positive ions such as xenon atoms move to the sustaining electrode 3b. With these processes, the lower face of the dielectric layer 6 formed under the sustaining electrode 3a is negatively charged and the lower face of the dielectric layer 6 formed under the sustaining electrode 3b is positively charged, and then the charge is stopped.
Recently, concerning general displays, also concerning an AC driving surface discharge type of PDP, it is required that an image quality is high and a power consumption is low.
However, in the conventional PDP 1, when a luminance is made high by increasing the voltage to be applied the sustaining electrode 3a and the sustaining electrode 3b in order to improve the image quality, the power consumption caused by the discharge increases.
Then, to carry out a high image quality and a low power consumption, though a first technique to a third technique are considered, new problems occur as follows.
First, to reduce the power consumption of the AC driving surface discharge type of PDP, it is necessary to improve a luminous efficiency of a display cell and to reduce a power consumed by the discharge. Generally, in the AC driving surface discharge type of PDP, as a discharge current density becomes low, a luminous efficiency of ultraviolet rays becomes high. As a result, a luminous efficiency of visible light tends to become high. Then, when a voltage to be applied to a sustaining electrode is reduced and a discharge current is reduced, the discharge current density becomes low. Therefore, it is possible to make a luminous efficiency of a display cell high. However, when the voltage to be applied to the sustaining electrode is reduced, the discharge becomes unstable, and therefore, it is impossible to carry out a stable display operation.
Secondly, when widths of the sustaining electrode 3a and the sustaining electrode 3b are made narrow and areas of the sustaining electrode 3a and the sustaining electrode 3b are reduced, it is possible to reduce a capacitance between the lower face of the dielectric layer 6, and the sustaining electrode 3a and the sustaining electrode 3b. When a voltage applied to the sustaining electrode 3a is equal to a voltage applied to the sustaining electrode 3b, a charge amount accumulated on the lower face of the dielectric layer 6 reduces when the charge is stopped. Therefore, it is possible to reduce a discharge current. However, in the second technique, as described above, since the areas of the sustaining electrode 3a and the sustaining electrode 3b are reduced, the discharge current density of the display cell 12 does not change after all, and therefore, the luminous efficiency hardly changes. Also, when the areas of the sustaining electrode 3a and the sustaining electrode 3b are reduced, the charge does not diffuse in the sustaining electrode 3a and the sustaining electrode 3b over all, and therefore, only a part of the fluorescent layer 14R, the fluorescent layer 14G, and the fluorescent layer 14B emits. As a result, a luminance of the display cell 12 gets worse, and it is impossible to obtain a sufficient image quality.
Thirdly, Japanese Patent Application Laid-open No. Hei 8-22772 discloses a following technique. In this technique, a sustaining electrode made up of a transparent conductive thin film includes a main part extending in a row direction and a projection part projecting from the main part to an adjacent sustaining electrode for each display cell. Then, the projection part has a narrow small part which a width in the row direction is narrower than a width of a top end part in the row direction. In this technique, the narrow small part is provided, whereby the discharge current for one display cell is reduced so as to reduce the power consumption. As a result, the luminous efficiency is improved. However, in this technique, since the discharge concentrates near the small narrow part and does not diffuse in the display cell over all, there is a possibility in that a luminance lowers. Also, in this technique, the sustaining electrode made up of the transparent conductive thin film is patterned in a complex shape, a crack occurs in the small narrow part and there is a possibility of breaking.
In view of the above, it is an object of the present invention to provide a plasma display panel and a method of manufacturing the plasma display panel capable of providing both a high image quality and a low power consumption.
According to a first aspect of the present invention, there is provided a plasma display panel having a plurality of surface discharge electrode pairs formed in a column direction at predetermined intervals, each of the surface discharge electrode pairs having a pair of sustaining electrodes extending in a row direction so that a discharge gap is put between the sustaining electrodes, wherein:
each of the sustaining electrodes is made up of a transparent conductive thin film main electrode portion formed in stripe shapes so as to face the discharge gap and a metal film of which a width is narrower than a width of the main electrode portion that forms a sub-electrode at a side of the main electrode opposite the discharge gap.
In the foregoing, a preferable mode is one wherein the sub-electrode portion is provided with a first parallel portion extending in the row direction at a predetermined distance from the main electrode portion, and a second parallel portion extending in the row direction at a predetermined distance from the first parallel portion between the main electrode portion and the first parallel portion.
Also, a preferable mode is one wherein the sub-electrode portion is provided with a vertical portion extending to the main electrode portion at a position at which distances from adjacent division walls extending in the column direction for separating each display cell are approximately equal and integrated with the first parallel portion and the second parallel portion in a manner that an end portion of the vertical portion is electrically in contact with the main electrode portion.
Also, a preferable mode is one wherein the sub-electrode portion is provided with a first vertical portion extending to the main electrode portion at a position at which distances from adjacent division walls extending in the column direction for separating each display cell are approximately equal and integrated with the first parallel portion and the second parallel portion in a manner that an end portion of the vertical portion is electrically in contact with the main electrode portion, and a second vertical portion extending to the main electrode portion in the column direction at an upper side of the division wall and integrated with the first parallel portion and the second parallel portion in a manner that an end portion of the second vertical portion is electrically in contact with the main electrode portion.
Also, a preferable mode is one wherein a width of the second vertical portion is equal to a width of the division wall or is narrower than the width of the division wall.
Also, a preferable mode is one wherein a width of the second vertical portion is a half of a width of the division wall or less.
Also, a preferable mode is one wherein a width of the second parallel portion is 1 xcexcm to 50 xcexcm.
Also, a preferable mode is one wherein a width of the second parallel portion is 1 xcexcm to 30 xcexcm.
Also, a preferable mode is one wherein a width of the first vertical parallel portion is 1 xcexcm to 50 xcexcm.
Also, a preferable mode is one wherein a width of the first vertical parallel portion is 1 xcexcm to 30 xcexcm.
Also, a preferable mode is one wherein the main electrode portion is provided with a main electrode parallel portion extending in the row direction, and a main electrode projection part projecting from the main electrode portion at a side opposite to the discharge gap side of the main electrode portion at a position at which distances from adjacent division wall extending in the column direction to separate each display cell are approximately equal, and the first vertical portion extends to the main electrode portion in the column direction perpendicular to the first parallel portion and the second parallel portion and is integrated with the first parallel portion and the second parallel portion in a manner that an end portion of the first vertical portion is electrically in contact with the main electrode portion which corresponds.
Also, a preferable mode is one wherein lengths of the main electrode projection part in the row direction and in the column direction are 30 xcexcm to 60 xcexcm.
Also, a preferable mode is one wherein the sub-electrode portion is provided with a first parallel portion extending in the row direction at a predetermined distance from the main electrode portion, a first vertical portion extending to the main electrode portion in the column direction over each division wall extending in the column direction so as to separate each display cell and integrated with the first parallel portion in a manner that an end portion of the first vertical portion is electrically in contact with the main electrode portion, and a cross part including a second vertical portion extending to the main electrode portion in the column direction at a position at which distances from adjacent division walls are approximately equal and an end portion of the second vertical portion reaching near a side face of the main electrode portion, and second parallel portions respectively extending from an approximate center to the first vertical portions which are adjacent in a manner that an end portion of each of the second parallel portions reaches near the first vertical portions which are adjacent, the cross part integrated with the first vertical portion.
Also, a preferable mode is one wherein a width of the first vertical portion is equal to a width of the division wall or is narrower than a width of the division wall.
Also, a preferable mode is one wherein a width of the first vertical portion is a half of a width of the division wall or less.
Also, a preferable mode is one further including:
a bus electrode portion including a bus electrode parallel portion extending in the row direction in parallel with the first parallel portion at a distance at which there is no influence from the first parallel portion, and a bus electrode vertical portion extending to the first parallel portion in the column direction perpendicular to the first parallel portion and the bus parallel portion in a manner that an end portion of the bus electrode vertical portion is electrically in contact with the first parallel portion, and the bus electrode portion is integrated with the sub-electrode portion.
Also, a preferable mode is one wherein a width of the main electrode portion is 30 xcexcm to 100 xcexcm.
Also, a preferable mode is one wherein a width of the main electrode portion is 40 xcexcm to 80 xcexcm.
Also, a preferable mode is one wherein widths of the first parallel portion and the second parallel portion are 30 xcexcm to 100 xcexcm.
Also, a preferable mode is one wherein widths of the first parallel portion and the second parallel portion are 40 xcexcm to 80 xcexcm.
Also, a preferable mode is one wherein a width of the first parallel portion is 30 xcexcm to 60 xcexcm.
Furthermore, a preferable mode is one wherein both of an interval between the main electrode portion and the first parallel portion, and an interval between the second parallel portion and the first parallel portion are 30 xcexcm to 140 xcexcm.
According to a second aspect of the present invention, there is provided a method of manufacturing a plasma display panel according to the first aspect, a method including:
a first step of coating photosensitive silver paste on a front insulation substrate or a front insulation substrate after forming a plurality of surface discharge pair; and
a second step of forming a sub-electrode portion by annealing after exposing and developing the photosensitive silver paste and patterning the photosensitive silver paste.
According to a third aspect of the present invention, there is provided a method of manufacturing a plasma display panel according to the first aspect, a method including:
a first step of coating silver paste on a front insulation substrate or a front insulation substrate after forming a plurality of surface discharge pair; and
a second step of forming the sub-electrode portion by annealing after patterning the silver paste.
With this configuration, it is possible to obtain a high image quality high and to reduce power consumption.